Bushfire smoke triggered blackout

Air thick with carbon: Thick smoke and ash swirling upwards from a burning pine plantation near the main power interconnector between Victoria and NSW began to drift across three high-voltage lines strung between transmission towers. Electricity arced through the carbon-laden air from one line to the next. A second arc is believed to have leapt from the line to the ground.

Auto shutdown avoids worse: The sensor on the tower immediately detected the fluctuation in electricity levels flowing down the lines to meet Victoria’s near-record demand for power on a day when temperatures had reached 40C and air-conditioners were running flat-out. The sensor flashed a message, warning of the sudden disruption, to a computer at the central control room that constantly monitors the line. The computer “tripped” the line, shutting it down to avoid the arcing causing serious damage to the wires or towers.

Demand 20pc above supply: Up to that point, Victorians had been using about 9500 megawatts in an attempt to beat the heat. In the blink of an eye that was reduced by 2000mW. With the demand for power suddenly exceeding supply by almost 20 per cent, the state’s automatic load-shedding program kicked in.

Power supply remains at risk: Deputy Premier John Thwaites yesterday warned that with fires still burning in many parts of the state, including the blaze near Benalla that triggered Tuesday’s crisis, similar blackouts could occur. This included fires in Gippsland in eastern Victoria, which could cause problems for transmission lines linking Melbourne with the state’s main power stations in the Latrobe Valley.